U.S. patent application number 13/749054 was filed with the patent office on 2013-08-01 for image-taking apparatus and method for controlling the same.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. The applicant listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Kentaro Kogure, Takamichi Nakata.
Application Number | 20130194469 13/749054 |
Document ID | / |
Family ID | 48869900 |
Filed Date | 2013-08-01 |
United States Patent
Application |
20130194469 |
Kind Code |
A1 |
Nakata; Takamichi ; et
al. |
August 1, 2013 |
IMAGE-TAKING APPARATUS AND METHOD FOR CONTROLLING THE SAME
Abstract
An image-taking apparatus changes a switching threshold value
for switching between a color mode and a monochrome mode according
to a maximum gain value set by a maximum gain setting unit so that
switching between the color and monochrome modes can be optimally
performed regardless of setting of the maximum gain value. The
image-taking apparatus includes a threshold value correction unit
configured to correct the switching threshold value according to
the maximum gain value. The threshold value correction unit sets
the switching threshold value with the maximum gain value set
larger than an initial value to be smaller than the switching
threshold value with the maximum gain value set smaller than the
initial value.
Inventors: |
Nakata; Takamichi;
(Kawasaki-shi, JP) ; Kogure; Kentaro; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA; |
Tokyo |
|
JP |
|
|
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
48869900 |
Appl. No.: |
13/749054 |
Filed: |
January 24, 2013 |
Current U.S.
Class: |
348/300 |
Current CPC
Class: |
H04N 5/2351 20130101;
H04N 9/68 20130101; H04N 5/23245 20130101 |
Class at
Publication: |
348/300 |
International
Class: |
H04N 9/68 20060101
H04N009/68 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 27, 2012 |
JP |
2012-015544 |
Nov 6, 2012 |
JP |
2012-244599 |
Claims
1. An image-taking apparatus comprising: a gain control unit
configured to control a gain for amplifying a signal from an
image-pickup sensor; an image data generation unit configured to
generate image data representing a subject image captured by the
image-pickup sensor; a switching unit configured to switch an
output of the image data generated by the image data generation
unit to either a color output or a monochrome output; a maximum
gain setting unit configured to set a maximum value of the gain
controlled by the gain control unit; a switching evaluation value
calculation unit configured to calculate a switching evaluation
value based on an output from the image data generation unit; a
determination unit configured to determine the switching of the
output of the image data by the switching unit based on a result of
comparison between the switching evaluation value and a switching
threshold value for switching the output of the image data to
either a color output or a monochrome output; and a threshold value
correction unit configured to correct the switching threshold value
according to the maximum gain value set by the maximum gain setting
unit, wherein the threshold value correction unit sets the
switching threshold value with the maximum gain value set larger
than an initial value to be smaller than the switching threshold
value with the maximum gain value set smaller than the initial
value.
2. The image-taking apparatus according to claim 1, wherein when a
subject luminance becomes low, the color output of the image data
is maintained for a longer time when the maximum gain value set by
the maximum gain setting unit is large than when the maximum gain
value set by the maximum gain setting unit is small.
3. The image-taking apparatus according to claim 1, further
comprising: a mode switching unit configured to switch between a
noise suppression priority mode and a sensitivity priority mode;
and a gain/amplification factor adjustment unit configured to
adjust the gain controlled by the gain control unit when the
switching unit switches the output of the image data to the color
output or the monochrome output.
4. The image-taking apparatus according to claim 3, wherein a
maximum amplification factor adjustable by the gain/amplification
factor adjustment unit is set, when the sensitivity priority mode
is set with the output of the image data set to the monochrome
output.
5. The image-taking apparatus according to claim 3, wherein an
amplification factor adjustable by the gain/amplification factor
adjustment unit increases as the maximum gain value set by the
maximum gain setting unit increases, when the noise suppression
priority mode is set with the output of the image data set to the
monochrome output.
6. A method for controlling an image-taking apparatus, the method
comprising: generating image data representing a subject image
captured by an image-pickup sensor; switching an output of the
generated image data to either a color output or a monochrome
output; setting a maximum value of a gain for amplifying a signal
from the image-pickup sensor; calculating a switching evaluation
value based on the output of the image data; determining the
switching of the output of the image data based on a result of
comparison between the switching evaluation value and a switching
threshold value for switching the output of the image data to
either a color output or a monochrome output; correcting the
switching threshold value according to the set maximum gain value;
and setting the switching threshold value with the maximum gain
value set larger than an initial value to be smaller than the
switching threshold value with the maximum gain value set smaller
than the initial value.
7. A non-transitory computer-readable storage medium storing a
program that causes a computer to perform a method comprising:
generating image data representing a subject image captured by an
image-pickup sensor; switching an output of the generated image
data to either a color output or a monochrome output; setting a
maximum value of a gain for amplifying a signal from the
image-pickup sensor; calculating a switching evaluation value based
on the output of the image data; determining the switching of the
output of the image data based on a result of comparison between
the switching evaluation value and a switching threshold value for
switching the output of the image data to either a color output or
a monochrome output; correcting the switching threshold value
according to the set maximum gain value; and setting the switching
threshold value with the maximum gain value set larger than an
initial value to be smaller than the switching threshold value with
the maximum gain value set smaller than the initial value.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present disclosure generally relates to an image-taking
apparatus and a control method therefor and, more particularly, to
those capable of appropriately switching an image output mode when
a maximum gain value is set.
[0003] 2. Description of the Related Art
[0004] A human color vision characteristic serving as a sensitivity
to a color and a human luminous efficiency characteristic serving
as a sensitivity to brightness fall within a range from 380 nm to
780 nm, which is referred to as a visible range. Humans have little
sensitivity in a longer wavelength range than 700 nm. Generally in
an image-taking apparatus, an infrared ray cut filter (IRCF) for
visibility correction, which does not pass a light beam in a
near-infrared region, is provided ahead of an image-pickup sensor
so that color reproducibility can match the human color vision
characteristic.
[0005] However, under low illumination at which a subject luminance
decreases, the IRCF is often removed from an optical path so that
the light beam in the near-infrared region is passed through the
optical path, to increase the sensitivity. When the light beam in
the near-infrared region is passed through the optical path,
however, a color balance is lost. Therefore, an imaging mode is
switched from a color image (a Day mode) to a monochrome image (a
Night mode). A switching method also includes a function of
automatically switching between a Day mode and a Night mode, which
is referred to as an auto Day/Night (hereinafter referred to as an
ADN).
[0006] In a lens having no IRCF insertion/removal mechanism, for
example, a varifocal lens, the sensitivity cannot be increased, but
noise that affects a color component can be removed. Therefore,
there is a camera for merely switching an imaging mode from a color
image to a monochrome image. A threshold value of the subject
luminance at the time of switching from the color image to the
monochrome image is determined based on automatic exposure (AE)
data (a shutter speed, an iris, automatic gain control (AGC), a
screen luminance) of the camera.
[0007] In recent years, cameras including a unit for setting a
maximum gain value have been available, so that a scene having a
screen a large part of which is black, e.g., a night scene can be
clearly photographed by limiting a gain value of an AGC
circuit.
[0008] An image-taking apparatus discussed in Japanese Patent
Application Laid-Open No. 2010-279061, for example, uses a method
for switching a mode by inserting or removing an infrared cut
filter according to a determination result of at least one of
outputs from an imaging unit and a luminosity detection unit.
[0009] However, in the configuration of the image-taking apparatus
discussed in Japanese Patent Application Laid-Open No. 2010-279061,
a maximum gain value cannot be set. On the other hand, in the
camera having a function of setting a maximum gain value that has
attracted a demand from a user in recent years, a determination
reference value is not appropriately set in response to an output
change according to the setting of the maximum gain value.
Therefore, a mode switching cannot be correctly performed.
SUMMARY OF THE INVENTION
[0010] The present disclosure is directed to an image-taking
apparatus capable of switching, with a simple configuration, an
image output mode when a maximum gain value is set.
[0011] According to an aspect of the present disclosure, an
image-taking apparatus includes a gain control unit configured to
control a gain for amplifying a signal from an image-pickup sensor,
an image data generation unit configured to generate image data
representing a subject image captured by the image-pickup sensor, a
switching unit configured to switch an output of the image data
generated by the image data generation unit to either a color
output or a monochrome output, a maximum gain setting unit
configured to set a maximum value of the gain controlled by the
gain control unit, a switching evaluation value calculation unit
configured to calculate a switching evaluation value based on an
output from the image data generation unit, a determination unit
configured to determine the switching of the output of the image
data by the switching unit based on a result of comparison between
the switching evaluation value and a switching threshold value for
switching the output of the image data to either a color output or
a monochrome output, and a threshold value correction unit
configured to correct the switching threshold value according to
the maximum gain value set by the maximum gain setting unit. The
threshold value correction unit sets the switching threshold value
with the maximum gain value set larger than an initial value to be
smaller than the switching threshold value with the maximum gain
value set smaller than the initial value.
[0012] According to another aspect of the present disclosure, a
method for controlling an image-taking apparatus includes
generating image data representing a subject image captured by an
image-pickup sensor, switching an output of the generated image
data to either a color output or a monochrome output, setting a
maximum value of a gain for amplifying a signal from the
image-pickup sensor, calculating a switching evaluation value based
on the output of the image data, determining the switching of the
output of the image data based on a result of comparison between
the switching evaluation value and a switching threshold value for
switching the output of the image data to either a color output or
a monochrome output, correcting the switching threshold value
according to the set maximum gain value, and setting the switching
threshold value with the maximum gain value set larger than an
initial value to be smaller than the switching threshold value with
the maximum gain value set smaller than the initial value.
[0013] According to exemplary embodiments of the present
disclosure, a switching threshold value for switching between a
color mode and a monochrome mode is changed according to the
maximum gain value, so that switching to the color or monochrome
mode can be optimally performed regardless of setting of a maximum
gain value.
[0014] Further features and aspects of the present disclosure will
become apparent from the following detailed description of
exemplary embodiments with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate exemplary
embodiments, features, and aspects of the disclosure and, together
with the description, serve to explain the principles of the
disclosure.
[0016] FIG. 1 illustrates a configuration of a camera according to
a first exemplary embodiment of the present disclosure.
[0017] FIG. 2 illustrates a configuration of an imaging unit in the
camera according to the first exemplary embodiment.
[0018] FIG. 3 is a flowchart illustrating processing of the camera
according to the first exemplary embodiment.
[0019] FIGS. 4A, 4B, and 4C each illustrate an image obtained when
a maximum gain value changes at the same exposure value (EV)
according to the first exemplary embodiment.
[0020] FIG. 5 illustrates a configuration of a camera according to
a second exemplary embodiment.
[0021] FIG. 6 is a flowchart illustrating processing of the camera
according to the second exemplary embodiment.
[0022] FIG. 7 illustrates an example of an amplification factor set
in a noise suppression priority mode according to the second
exemplary embodiment.
DESCRIPTION OF THE EMBODIMENTS
[0023] Various exemplary embodiments, features, and aspects of the
disclosure will be described in detail below with reference to the
drawings.
[0024] A case where a camera is used as an image-taking apparatus
will be described below.
[0025] FIG. 1 illustrates a configuration of a camera according to
a first exemplary embodiment of the present disclosure.
[0026] The camera includes an image data generation unit 101
configured to receive light from outside the camera to generate
image data. The image data generation unit 101 includes an imaging
unit 102 and an image signal processing unit 103 configured to
subject a signal obtained from the imaging unit 102 to
predetermined processing.
[0027] The camera includes an imaging mode switching unit 104
configured to switch image data to a monochrome image or a color
image, and a switching evaluation value calculation unit 105
configured to calculate an evaluation value based on an output from
the imaging unit 102. Further, the camera includes a maximum gain
setting unit 107 capable of setting a maximum value of a gain by a
user's operation, and a threshold value correction unit 108
configured to correct a predetermined switching threshold value for
monochrome/color mode switching. The camera also includes an
imaging mode determination unit 106 configured to determine the
switching of the image data by the imaging mode switching unit 104
based on a result of comparison between the switching evaluation
value and the switching threshold value for switching an output of
the image data to either a color output or a monochrome output.
[0028] In addition, the camera includes a display unit 109
configured to display the image data output from the imaging mode
switching unit 104 based on the result of comparison between the
switching evaluation value and the switching threshold value.
[0029] FIG. 2 illustrates a detailed configuration of the imaging
unit 102.
[0030] The imaging unit 102 includes a lens 201 including several
lens groups, a driving unit (not illustrated), an IRCF 202, which
can be inserted and removed with respect to the lens 201 by the
driving unit, and an image-pickup sensor 203, such as a charge
coupled device (CCD) sensor or a complementary metal oxide
semiconductor (CMOS) sensor. Further, the imaging unit 102 further
includes a correlated double sampling (CDS) circuit 204 configured
to reduce noise. The imaging unit 102 further includes an AGC
circuit 205 configured to automatically control the gain of the
camera.
[0031] In addition, the imaging unit 102 includes an
analog-to-digital (A/D) converter 206 configured to convert an
analog signal into a digital signal.
[0032] An operation of each of the above-mentioned constituent
elements will be described in detail.
[0033] The image data generation unit 101 will be first described
in detail with reference to FIGS. 1 and 2.
[0034] The image-pickup sensor 203 converts a subject image formed
via the lens 201 serving as an imaging optical system and the IRCF
202 into an electric signal. The CDS circuit 204 performs
correlated double sampling processing for the electric signal
output from the image-pickup sensor 203. The AGC circuit 205
performs amplification processing for the electric signal output
from the CDS circuit 204. The A/D converter 206 converts an analog
signal, which has been subjected to the amplification processing by
the AGC amplifier 205, into a digital signal.
[0035] The image signal processing unit 103 includes a digital
signal processor (DSP), for example, and performs predetermined
image processing on the digital signal, such as color conversion,
AE processing, white balance (WB) processing, and gamma processing
for performing gradation conversion of a signal-processed
image.
[0036] The image data output from the image data generation unit
101 is input to the imaging mode switching unit 104, and is output
after being converted into a monochrome image or a color image.
While the imaging mode switching unit 104 is independently
illustrated, the image signal processing unit 103 may include the
imaging mode switching unit 104.
[0037] To switch between a monochrome image and a color image, the
switching evaluation value calculation unit 105 calculates a
switching evaluation value from imaging conditions such as a
diaphragm, a shutter speed, and a gain, which have been output from
the imaging unit 102. The switching between the monochrome image
and the color image may be referred to as a Day/Night function.
Therefore, in the present exemplary embodiment, an imaging mode of
the camera is referred to as a Night mode for the monochrome image
and a Day mode for the color image. The mode switching is
hereinafter referred to as a Day/Night mode switching.
[0038] In the maximum gain setting unit 107 capable of setting the
maximum value of the gain, a maximum gain value can be set. The
maximum gain value indicates to what extent degradation due to a
component such as noise or a sharpness feeling of an image can be
permitted. For example, the setting may be opened to the user so
that the user can optionally determine the setting or the setting
can be automatically changed according to an internal state of the
camera.
[0039] The threshold value correction unit 108 corrects a
predetermined threshold value, for a predetermined Day/Night mode
switching, to be the most suitable switching threshold value
according to the maximum gain value set by the maximum gain setting
unit 107.
[0040] The imaging mode determination unit 106 receives inputs from
the switching evaluation value output by the switching evaluation
value calculation unit 105 and the threshold value corrected by the
threshold value correction unit 107, to determine which of the Day
mode and the Night mode is used for the imaging mode switching unit
104 to output the image. If the switching evaluation value is
smaller than the switching threshold value, for example, the image
is output in the Night mode.
[0041] In the present exemplary embodiment, the imaging unit 102
includes the IRCF 202. When it is determined that the monochrome
image is output to the switching unit 104, a signal is output to an
IRCF driving unit (not illustrated). Then, in the IRCF driving
unit, the IRCF 202 is removed from an optical path of the imaging
optical system to receive an infrared component, to increase a
subject luminance.
[0042] The image display unit 109 includes a liquid crystal display
(LCD), for example, and displays the image data output from the
switching unit 104.
[0043] With reference to a flowchart illustrated in FIG. 3,
operation processing for switching the imaging mode of the camera
from the Day mode to the Night mode will be described. If the
imaging mode is the Day mode, the image data is output as a color
image. The image data generation unit 101, the imaging mode
switching unit 104, the switching evaluation value calculation unit
105, the imaging mode determination unit 106, the maximum gain
setting unit 107, and the threshold value correction unit 108
mainly operate so that processing illustrated in the flowchart is
implemented.
[0044] In step S301, the imaging mode switching unit 104 first
acquires the image data output from the image data generation unit
101.
[0045] In step S302, the switching evaluation value calculation
unit 105 calculates the switching evaluation value based on imaging
conditions, i.e., a diaphragm value, a shutter speed, and an AGC
gain value, which have been output from the imaging unit 102 in the
image data generation unit 101.
[0046] An example of a method for calculating the switching
evaluation value is illustrated below. A switching evaluation value
S is expressed by the following equation:
S=iris+shutter+AGC gain
[0047] where iris, shutter, AGC gain are respectively the diaphragm
value, the shutter speed, and the AGC gain value. Their respective
values are illustrated below.
[0048] The switching evaluation value S is a value representing
brightness in exposure, i.e., an EV. The EV is a logarithmic
expression of each of the diaphragm value (F-number), the shutter
speed (sec), and the AGC gain value (dB). The switching evaluation
value S illustrated above is an example. The switching evaluation
value S is also expressed by the following equation when a gain is
applied by the image signal processing unit 103:
S=iris+shutter+AGC gain+gain applied by image signal processing
unit
[0049] Thus, the switching evaluation value S can have various
formats within the scope of the present disclosure.
[0050] In step S303, the threshold value correction unit 108
corrects a predetermined switching threshold value according to the
maximum gain value, which is previously set by the user in the
maximum gain setting unit 107. The predetermined switching
threshold value may be a default value incorporated into the
camera, or may be an optional value determined by the user. While
the maximum gain value is to be optionally set by the user in the
present exemplary embodiment, the value can be automatically set
according to an imaging condition and a subject.
[0051] In step S304, the imaging mode determination unit 106
determines which of the switching evaluation value output by the
switching evaluation value calculation unit 105 and the switching
threshold value output by the threshold value correction unit 108
is larger. If the switching evaluation value is smaller than the
switching threshold value (YES in step S304), i.e., if a subject
having a low luminance is imaged, then in step S305, the imaging
mode switching unit 104 switches the imaging mode to the Night
mode. On the other hand, if the switching evaluation value is not
smaller than the switching threshold value (NO in step S304), then
in step S306, the imaging mode switching unit 104 maintains the Day
mode.
[0052] An operation for switching from the Night mode (monochrome
output) to the Day mode (color output) can also be implemented
similarly to the above-mentioned operation. If the switching
evaluation value is larger than the switching threshold value, the
Night mode is switched to the Day mode. Further, if the camera
includes the imaging unit 102 illustrated in FIG. 2, the IRCF 202
is removed from the optical path, simultaneously with switching to
the Night mode, using the IRCF driving unit (not illustrated). On
the other hand, the IRCF 202 is arranged again on the optical path,
when switching to the Day mode.
[0053] An example of the present exemplary embodiment will be
described with reference to FIGS. 4A to 4C.
[0054] The basic idea in the present exemplary embodiment will be
first described with reference to FIGS. 4A to 4C. FIGS. 4A to 4C
each illustrate an image of the subject obtained when the maximum
gain value is changed at the same EV. The EV at this time is
sufficiently small, and the image is not correctly exposed even
when the maximum gain value is large (as illustrated in FIG. 4C).
If the maximum gain value increases, the sensitivity also increases
in proportion thereto. Therefore, the image brightness increases in
the order of images in FIGS. 4A, 4B, and 4C. Similarly, if the
maximum gain value increases, noise also increases. Therefore, the
noise feeling becomes worse in the order of images in FIGS. 4A, 4B,
and 4C.
[0055] Thus, the top image is low in sensitivity, and immediately
disappears from view. Therefore, the switching threshold value for
switching the imaging mode is set to be large. On the other hand,
the bottom image is high in sensitivity, with a worse noise
feeling. However, a range in which the subject can be recognized
increases. Therefore, the bottom image is to be captured in the
color mode for as long a time as possible. Thus, the switching
threshold value is set to be small.
[0056] A more specific operation will be described below with
reference to FIGS. 4A to 4C.
[0057] FIG. 4B illustrates an image obtained when the maximum gain
value is set to an initial value. The image is intermediate in both
noise feeling and brightness among the images illustrated in FIGS.
4A to 4C.
[0058] FIG. 4C illustrates an image captured in a case where the
maximum gain setting unit 107 sets the maximum gain value to be
larger than the initial value. FIG. 4C illustrates a state where a
subject luminance is low at night and a gain value automatically
reaches the maximum gain value. At this time, a noise amount
becomes high, although the subject image becomes bright. In the
state illustrated in FIG. 4C, a switching threshold value is
decreased because the maximum gain value is set larger than the
initial value.
[0059] Thus, the subject image can be captured in the color mode
for a longer time than when the maximum gain value is set to the
initial value. However, the gain value also increases by an amount
corresponding to a rise in sensitivity, so that a noise component
increases. The increase in the noise component constitutes a factor
of significant deterioration in image recognition property.
[0060] To perform more effective monitoring, a switching threshold
value may be changed by the user's setting. When a color component
of the image is attached importance as an example, the switching
threshold value is decreased from the initial value. On the other
hand, when a recognition property of the subject is significantly
decreased by the image deterioration due to the noise, the
switching threshold value may remain at the initial value.
[0061] On the other hand, FIG. 4A illustrates an image captured in
a case where the maximum gain setting unit 107 sets the maximum
gain value to be smaller than the initial value. Thus, the noise
component is smaller than that when the maximum gain value is set
comparatively large. However, the brightness of a screen is high.
At this time, when the screen becomes darker, the subject entirely
disappears from view. Therefore, the sensitivity needs to be
increased by early switching the imaging mode to the Night mode to
remove the IRCF 202. Thus, the switching threshold value is set to
be large.
[0062] The threshold value correction unit 108 corrects a
predetermined switching threshold value according to a setting
value of the maximum gain, so that the imaging mode can be switched
when the image achieves a desired image quality, according to the
present exemplary embodiment.
[0063] There can be a method for automatically acquiring a
switching threshold value from a switching threshold value table
according to setting of a maximum gain value or a method for
automatically setting a switching threshold value by automatically
adding and subtracting an EV of a difference from the initial
maximum gain value to and from its initial switching threshold
value. Alternatively, the user may manually set the threshold
value.
[0064] A second exemplary embodiment of the present disclosure will
be described below.
[0065] FIG. 5 illustrates a configuration of a camera according to
the second exemplary embodiment. In the second exemplary
embodiment, constituent elements added to those in the first
exemplary embodiment are mainly described, and similar constituent
elements to those in the first exemplary embodiment are assigned
with the same reference numerals, and hence description thereof is
not repeated.
[0066] The camera includes a gain/amplification factor adjustment
unit 501 configured to adjust an amplification factor serving as a
gain of an image during switching and a priority mode switching
unit 502 configured to switch a priority mode.
[0067] The gain/amplification factor adjustment unit 501 receives a
Day/Night switching signal from an imaging mode switching unit 104,
and simultaneously adjusts the gain of the image therewith. The
gain amplification adjustment unit 501 also amplifies image data
based on an amplification factor from the priority mode, which has
been optionally set by a user, by the priority mode switching unit
502.
[0068] In the present exemplary embodiment, a WB gain is used as a
gain control means, which is used by the gain/amplification factor
adjustment unit 501. More specifically, the WB gain at which a
color balance of the image is controlled in the image signal
processing unit 103 is not required when a screen becomes
monochrome in a Night mode.
[0069] The priority mode includes two modes, i.e., a sensitivity
priority mode and a noise suppression priority mode. The two
priority modes are used when the gain value is set to a value equal
to or greater than the set maximum gain value to further increase
the sensitivity in the Night mode. If the sensitivity is to be
increased, the sensitivity priority mode is set. If a noise amount
is to be suppressed or is to be manually set, the noise suppression
priority mode is set.
[0070] In the sensitivity priority mode, the amplification factor
controlled by the WB gain is maximized regardless of the set
maximum gain value. If the amplification factor controlled by the
WB gain is to be a maximum of two times, for example, the maximum
gain value in the Night mode with any setting of the maximum gain
value, is obtained by adding 6 dB to the maximum gain value in the
Day mode so that the amplification factor in the Night mode is
uniformly two times the amplification factor in the Day mode. The
gain is calculated using the following equation:
x(dB)=20*log 10(y(times))
[0071] Therefore, the gain value is to be 6 dB if the amplification
factor is two times.
[0072] More specifically, the sensitivity priority mode is a mode
for adding a gain to its maximum regardless of a noise amount, to
ensure the maximum brightness of a screen. If the priority mode is
set to the sensitivity priority mode with an output of the image
data set to a monochrome output, the maximum amplification factor,
which can be automatically adjusted by the gain/amplification
factor adjustment unit 501, is set.
[0073] More specifically, when the maximum gain value set in the
Night mode is 18 dB, the amplification factor in the Night mode is
controlled to two times the amplification factor in the Day mode.
When the maximum gain value set in the Night mode is 24 dB, the
amplification factor in the Night mode is controlled to two times
the amplification factor in the Day mode. When the maximum gain
value set in the Night mode is 30 dB, the amplification factor in
the Night mode is controlled to two times the amplification factor
in the Day mode.
[0074] The noise suppression priority mode is a mode for varying
the amplification factor controlled by the WB gain according to the
set maximum gain value or for manually controlling the
amplification factor controlled by the WB gain.
[0075] Alternatively, in the noise suppression priority mode, even
if the Day mode is switched to the Night mode, the same maximum
gain value as that in the Day mode may be maintained without adding
an amount corresponding to the WB gain that is not required in the
Night mode.
[0076] FIG. 7 illustrates an example of a control method performed
when the amplification factor controlled by the WB gain is two
times, for example. When the set maximum gain value changes, as
illustrated in FIG. 7, the amplification factor controlled by the
WB gain is controlled to change in proportion thereto.
[0077] In FIG. 7, when the maximum gain value set in the Night mode
is 18 dB, the amplification factor in the Night mode is controlled
to 1.1 times the amplification factor in the Day mode. When the
maximum gain value set in the Night mode is 24 dB, the
amplification factor in the Night mode is controlled to 1.3 times
the amplification factor in the Day mode.
[0078] When the maximum gain value set in the Night mode is 30 dB,
the amplification factor is controlled to 1.5 times. Thus, at the
set maximum gain value in the Night mode, the amplification factor
is set so that a balance between noise and brightness becomes most
suitable. Alternatively, the user may set to what extent a gain is
applied in the Night mode to the set maximum gain value.
[0079] With reference to a flowchart illustrated in FIG. 6,
operation processing for the camera to switch the imaging mode from
the Day mode to the Night mode will be described below. In the
flowchart illustrated in FIG. 6, processing steps corresponding to
those in the flowchart illustrated in FIG. 3 are assigned with the
same step numbers, and hence description thereof is omitted.
[0080] First, steps S301 to S304 are similar to those in the first
exemplary embodiment, and hence description thereof is not
repeated. In step S601, the imaging mode determination unit 106
determines whether the priority mode set by the priority mode
switching unit 502 is the sensitivity priority mode. If the
priority mode is set to the sensitivity priority mode (YES in step
S601), then in step S602, the priority mode switching unit 502 sets
a predetermined amplification factor. In step S603, the set
amplification factor is input to the gain/amplification factor
adjustment unit 501 where the image data is amplified based on the
set amplification factor.
[0081] If the priority mode is set to the noise suppression
priority mode (NO in step S601), then in step S604, the
gain/amplification factor adjustment unit 501 sets the
amplification factor based on the maximum gain value. In step S603,
the gain/amplification factor adjustment unit 501 then amplifies
the image data according to the set amplification factor.
[0082] While the present disclosure has been described together
with various exemplary embodiments, the present disclosure is not
limited to the exemplary embodiments, and changes are made within
the scope of the present disclosure. For example, in the
above-mentioned exemplary embodiments, a digital still camera and a
digital video camera can be applied to the camera described as an
image-taking apparatus.
[0083] In the first and second exemplary embodiments, the image
signal processing unit 103, the imaging mode switching unit 104,
the switching evaluation value calculation unit 105, the imaging
mode determination unit 106, the maximum gain setting unit 107, the
threshold value correction unit 108, the gain/amplification factor
adjustment unit 501, and the priority mode switching unit 502 may
be implemented by a central processing unit (CPU) executing a
program.
[0084] More specifically, the units constituting the image-taking
apparatus according to the present exemplary embodiment and the
steps constituting the method for controlling the image-taking
apparatus can also be implemented by operating a program stored in
a memory of a computer. The present disclosure includes the program
and a computer-readable storing medium that stores the program.
[0085] In the present disclosure, an exemplary embodiment serving
as a system, an apparatus, a method, a program, or a storage medium
can also be realized. More specifically, the present disclosure may
be applied to a system including a plurality of apparatuses.
[0086] In the present disclosure, a program for implementing a
function of the above-mentioned exemplary embodiments may be
supplied directly or remotely to the apparatus or the system. More
specifically, the present disclosure may also be achieved when a
computer in the system or the apparatus reads out and executes the
supplied program.
[0087] Aspects of the present disclosure can also be realized by a
computer of a system or apparatus (or devices such as a CPU, a
micro processing unit (MPU), and/or the like) that reads out and
executes a program recorded on a memory device to perform the
functions of the above-described embodiment(s), and by a method,
the steps of which are performed by a computer of a system or
apparatus by, for example, reading out and executing a program
recorded on a memory device to perform the functions of the
above-described embodiment(s). For this purpose, the program is
provided to the computer for example via a network or from a
recording medium of various types serving as the memory device
(e.g., a non-transitory computer-readable medium).
[0088] While the present disclosure has been described with
reference to exemplary embodiments, it is to be understood that the
disclosure is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all modifications, equivalent
structures, and functions.
[0089] This application claims priority from Japanese Patent
Applications No. 2012-015544 filed Jan. 27, 2012 and No.
2012-244599 filed Nov. 6, 2012, which are hereby incorporated by
reference herein in their entirety.
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